Prime Scholars Library Advances in Agronomy, Plant Breeding and Horticulture Vol. 8 (3), pp.28 - 30, June, 2020 ©Prime Scholars Library SHORT COMMUNICATION Author(s) retain the copyright of this article. Article remain permanently open access under CC BY-NC-ND license Available online at https://creativecommons.org/licenses/by-nc-nd/4.0/ https://primescholarslibrary.org/ Determination of the chromosome number and karyotype of Platostoma africanum P. Beauv. Malik Z. H and Malik N. Z Department of Genetics and Biotechnology, University of Calabar, P. M. B 1115, Calabar, Cross Rivers State, Nigeria. Abstract Platostoma africanum P. Beauv. is a tropical plant species valued for its efficacy in traditional medicinal system in West Africa. Although studied for its chemical properties, no cytogenetic study has been reported on this plant species. Axillary buds obtained from the growing plants were used to conduct mitotic study. Results obtained in this study showed that P. africanum is a diploid species with chromosome number, 2n = 10. The mean chromosome length was 3.93 µm and chromosomes ranged from 3.08 to 5.39 µm, with a haploid set length of 19.64 µm. The karyotype showed assymetry with a formula, 1m+1sm+2a+1t and indicated good adaptation and advancement in evolution in this species. This is the first report of the chromosome number in this indigenous medicinal plant species. Keywords: Cytology, mitosis, medicinal plants, Lamiaceae. INTRODUCTION Platostoma africanum P. Beauv. belong to the plant symptoms. In Ghana, the leaves and seeds are used for family Lamiaceae and share some phenotypic similarities children’s coughs. It is also chewed with salt for sore with Ocimum species, also in the same family. At least 45 throat and its juice squeezed in the eyes for headache species are recognized in the genus Plastostoma spp. and fever. It is used for stomach medicine in Liberia found in tropical Africa, Madagascar, Tropical Asia and (Dalziel, 1948; von Reis and Lipp, 1982). Hexane and Northern Queensland (Paton, 1997). P. africanum is an dichloromethane extracts of the plant have been reported indigenous African herb known variously as “Akan- to have anti-inflammatory and antioxidant activities Osante” (Ghana), “Akan-brong”, “Guere” “Kru Guere” and (Aladedunye et al., 2008). It has also been found to Kyama (Ivory Coast), “Mani” (Liberia), “Manding-bambara contain a chromene derivative, precocene I, an insect (Senegal) (Burkill, 1985) and “Mkpri Ibok-ukpong” (Efik- anti-juvenile hormone (Onayade et al., 1989). Nigeria). It is widely found in damp sites and waste Although useful in local medicine, this species is largely places in Tropical African countries with a mildly aromatic uncultivated and undomesticated. However, with the slight mint or sage odor. The leaves are ovate, acute or discovery of rare essential oil constituents such as abruptly acuminate, with serrated margins at the upper monoterpenes, diterpenes and acidic pentacyclic portion, entire and wedge-shaped at the base, triterpenes (Aladedunye et al., 2008; Onayade et al., terminating with petioles that are 2 to 4 cm long 1989), commercial exploitation of this species is (Akobundu and Agyakwal, 1998). P. africanum has inevitable. In this regards, therefore, genetic slender racemes of very small flowers with white corolla. improvement of the species for greater recovery of P. africanum is used extensively in local traditional essential oil from the plants will become necessary. The medicine in West Africa. In Nigeria, it is used in the lack of basic genetic information on this species poses treatment of rheumatic symptoms, internal heat and serious limitation to its genetic improvement. This study leaves are used as a local haemostatic. It is also was therefore carried out to determine the chromosome sometimes used like Ocimum for fever; root mixed with number and karyotype of this species in order to provide Tephrosia linearis (Leguminosae) to make a decoction necessary information for its subsequent genetic used internally and externally for feverish chills, rheumatic improvement. Mag × 4200 Mag × 5600 Mag. x4200 Mag. x5600 Figure 1. Somatic metaphase of P. africanum showing chromosome number, 2n = 10. Table 1. Karyotype details of P. africanum (2n=10). Chromosome Long arm (µm) Short arm (µm) Total length (µm) Arm ratio Relative length (%) 1 3.85 1.54 5.39 2.5 27.44 2 3.08 1.16 4.24 2.7 2.59 3 2.31 1.54 3.85 1.5 19.60 4 3.08 - 3.08 0 15.68 5 1.54 1.54 3.08 1.0 15.68 Mean 2.77 1.16 3.93 MATERIALS AND METHODS RESULTS AND DISCUSSION Plant materials Five pairs of chromosomes were observed for this plant Plant samples, identified and confirmed in the herbarium in the species (Figure 1). The result indicated that the species Department of Botany, University of Calabar, Nigeria, were grown has a chromosome count of 2n = 10, having a karyotype at the Biological Sciences Building of the University of Calabar in formula of 1m+1sm+2a+1t with a haploid set length of Cross River State, Southeastern Nigeria (Long. 008°21' E, Lat. 19.64 µm (Tables 1 and 2). Mean total length of 04°47'N 4° 56´ N, 155 m above sea level). chromosome was 3.93 µm with chromosome size ranging from 3.08 µm (chromosome 3) to 5.39 µm Karyotype study (chromosome 1). The shortest chromosome constituted 15.68% of the genome with the longest occupying Axillary buds were obtained from the growing plants and pretreated 27.44% of the genome. The mean lengths of the short in 8-hydroxyquinoline (0.002M), fixed in Carnoy’s solution and and long arms were 1.16 and 2.77 µm, respectively. hydrolyzed in 1N hydrochloric acid at 60°C. The hydrolyzed The cytogenetic details obtained from this study shows materials were rinsed in 70% alcohol and stained with FLP Orcein that Platostoma africanum has an asymmetrical before squashing and viewing under a light microscope digitized karyotype. This is in accordance with Stebbins (1971) with a Chinese made power shot A630 Canon camera (8.0 megapixel, Canon PC 1201, NO 4126202101). Photographs of who described asymmetrical karyotypes as those good cells were taken. Chromosomes, repeatedly observed and possessing many chromosomes with sub-terminal counted from ten metaphase cells, were measured using R1370-19 centromeres or greater differences in size between the ocular micrometer calibrated with OB2001 objective micrometer at longest and smallest chromosomes. The higher 0.77 µm per unit and the idiogram of the species was accordingly proportion of acrocentric (40%) chromosomes as constructed. Description of chromosomes was based on size, arm length, haploid set length, relative length, symmetry and form compared to metacentric (20%) chromosomes also (Levan and Sandra, 1964; Pedro and Delgado, 2009; Vargas et al., depicts that the plant species is not primitive. Levitzky 2007. (1931) posited that chromosomes become more Table 2. Karyotype form of P. africanum (%). Conclusion Form Percentage In this study P. africanum has a chromosome count of 2n Metacentric 20 = 10, with chromosomes ranging in size from 3.08 to 5.39 Sub-metacentric 20 µm (Figure 2). This study has further revealed that the Acrocentric 40 plant species has an asymmetrical karyotype, indicative Telocentric 20 of advancement in its evolutionary trend. Karyotype formula – 1m+1sm+2a+1t. REFERENCES Akobundu IO, Agyakwal CW (1998). A Handbook of West African Weeds. IITA, Ibadan, Nigeria. Aladedunye FA, Okorie DA, Ighodaro OM (2008). Anti-inflammatory and antioxidant of constituents of Platostoma africanum. Natl. Prod. Resour., 22(12): 1067-1073. Burkill HM (1985). Platostoma africanum. Useful Plants of West Tropical Africa 3. Dalziel J (1948). The Useful Plants of West Tropical Africa. Crown Agents, London U.K. Levan AF, Sandra AA (1964). Nomenclature for lantromere position of chromosomes. Hereditas, 52: 201-220. Levitzky GA (1931). Bulletin of Applied Botany, Genetics and Plant Breeding, 27: 220-239. Maretti A, Sabato S (1984). Karyotype evolution by centromeric fission in Zamia (Cycadales). Plant Systematics Evolution, 146: 215-223. Onayade OA, Looman A, Scheffer JJ, Svendson AB (1989). Procene I and other Constituents of the essential oil Platostoma africanum. Planta med., 55(6): 553-555. Pedro M, Delgado-Salinas A (2009). Karyotype analysis in six species of Phaseolus. Caryologia, 62(3): 167-170. Stebbins GL (1971). Chromosomal evolution in higher plants. Edward Arnold, London. Vargas SM, Torres GA, Sobrinho FS, Pereira M, Davide LC (2007). Figure 2. Idiogram of P. arricanum (2n=10). Karyotype studies of Catylia argentea (Desv.), C. kuntze and C. mollis. J. Genetics Mole. Res., 6(3): 707-712. Von Reis S, Lipp Jr FJ (1982). New Plant Sources for Drugs and Foods from the New York Botanical Garden Herbarium. Harvard University Press, Cambridge MA. asymmetrical as evolution progresses, moving from sub- metacentric state to acrocentric state in extreme cases. It is known that increased asymmetry of the karyotype through shift of centromere positions, change in relative size of chromosomes in the complement as reported in this study are among trends observed in plant species as they show specialization and adaptation to their environment (Stebbins, 1971). A similar situation observed in this study was reported in Zamia paucijuga (Cycadales) where the strongly asymmetrical karyotype indicated recent evolution (Maretti and Sabato, 1984). .